Process for fabricating organic circuits

ABSTRACT

An organic semiconductor film is fabricated by applying a solution containing an organic semiconductor material and a solvent to a substrate, e.g., by solution casting, and evaporating the solvent. The characteristics of the substrate surface, the organic semiconductor material, and the process parameters are selected to provide desirable nucleation and crystal growth. The resultant organic semiconductor film contains a large area, e.g., a continuous area greater than 1 cm 2 , that exhibits a relatively high charge carrier mobility of at least about 10 −4  cm 2 V −1 s −1  room temperature.

BACKGROUND OF THE INVENTION

[0001] 1. Field of the Invention

[0002] The invention relates to fabrication of organic circuits such ascircuits containing organic thin film transistors.

[0003] 2. Discussion of the Related Art

[0004] Organic thin film transistors (TFTs) are expected to become keycomponents of the plastic circuitry in, among other things, displaydrivers of portable computers and pagers, and memory elements oftransaction cards and identification tags. A typical organic TFT isshown in FIG. 1. The TFT contains a source electrode 10, a drainelectrode 12, a gate electrode 14, a gate dielectric 16, a substrate 18,and the semiconductor material 20. When the TFT operates in anaccumulation mode, the charges injected from the source 10 into thesemiconductor are mobile and conduct the source-drain channel current,mainly in a thin channel region within about 100 Angstroms of thesemiconductor-dielectric interface. (See, e.g., M. A. Alam et al., “ATwo-Dimensional Simulation of Organic Transistors,” IEEE Transactions onElectron Devices, Vol. 44, No. 8 (1997).) In the configuration of FIG.1, the charge need only be injected laterally from the source 10 to formthe channel. In the absence of a gate field, the channel ideally has fewcharge carriers, and there is ideally no source-drain conduction. Theoff current is defined as the current flowing between the source 10 andthe drain 12 when charge has not been intentionally injected into thechannel by the application of a gate voltage, and for an accumulationmode TFT, this occurs for a gate-source voltage more positive (forp-channel) or negative (for n-channel) than a certain voltage known asthe threshold voltage. (See, e.g., S. M. Sze, SemiconductorDevices—Physics and Technology, John Wiley & Sons (1985).) The oncurrent is defined as the current flowing between the source 10 and thedrain 12 when the channel is conducting. For a p-channelaccumulation-mode TFT, this occurs at a gate-source voltage morenegative than the threshold voltage, and for an n-channel accumulationmode TFT, this occurs at gate-source voltage more positive than thethreshold voltage. It is desirable for this threshold voltage to bezero, or slightly positive, for n-channel operation. Switching betweenon and off is accomplished by the application and removal of an electricfield from the gate electrode 14 across the gate dielectric 16 to thesemiconductor-dielectric interface, effectively charging a capacitor.

[0005] One of the most significant factors in bringing such TFTs intocommercial use is the ability to deposit organic semiconductingmaterials on a substrate quickly and easily (i.e., inexpensively), ascompared to silicon technology, e.g., by reel-to-reel printingprocesses. Yet, in order to exhibit suitable electrical properties, theorganic materials need to be deposited as thin, uniform, crystallinefilms, which is a difficult task when using easy, inexpensive processes.(See, e.g., C. Cai et al., “Self Assembly in Ultrahigh Vacuum: Growth ofOrganic Thin Film with a Stable In-Plane Directional Order,” J. Am.Chem. Soc., Vol. 120, 8563 (1998).)

[0006] Thus, those in the art have sought to attain the necessaryuniformity and order in an organic semiconductor film by the easiestpossible fabrication techniques. Cai et al., supra, use an organicmolecular beam deposition technique to attain an ordered film, but sucha technique is not feasible for large-scale fabrication of organiccircuits. Other groups have used a polytetrafluoroethylene layer as atemplate for an organic semiconductor layer, but the organic material isdeposited by a vapor phase method which, again, is unsuitable forinexpensive commercial-scale fabrication. (See, e.g., P. Damman et al.,“Morphology and NLO properties of thin films of organic compoundsobtained by epitaxial growth,” Optical Materials, Vol. 9, 423 (1998);and P. Lang et al., “Spectroscopic Evidence for a Substrate DependentOrientation of Sexithiophene Thin Films Deposited onto Oriented PTFE,”J. Phys. Chem. B, Vol. 101, 8204 (1997).)

[0007] As suggested in Cai et al., supra, liquid phase techniques arethe most desirable for fabrication of organic TFTs, since they involvesimply providing the organic material in solution, depositing thesolution on a substrate, and removing the solvent. Such liquid phasetechniques have been somewhat successful for polymeric semiconductormaterials, as reflected, for example in Z. Bao et al., “High-PerformancePlastic Transistors Fabricated by Printing Techniques,” Chem. Mater.,Vol. 9, 1299 (1997); and H. Sirringhaus et al., “IntegratedOptoelectronic Devices Based on Conjugated Polymers,” Science, Vol. 280(1998). However, polymeric semiconductor materials tend to be highlysensitive to the fabrication conditions, are difficult to purify to theextent required for high mobilities and on/off ratios, and exhibitsubstantial batch-to-batch variability. Oligomeric materials and/orpolymers of relatively low molecular weight, and other low molecularweight compounds, tend to be less sensitive and are generally able to bepurified such that high, and less environmentally sensitive, mobilitiesand on/off ratios are possible. Thus, liquid phase techniques fordepositing low molecular weight compounds, such as oligomericsemiconductor materials and low molecular weight polymeric materials,are of particular interest.

[0008] For example, several groups have experimented with solutioncasting of thiophene oligomer films, in which a solution of the organicmaterial is essentially dropped onto a substrate, and the solvent isevaporated by heating. However, these processes have generally providedrelatively poor uniformity and coverage from such oligomeric solutioncasting. Relatively large areas, e.g., greater than 1 cm², exhibitinguseful semiconductor properties have thus been difficult to attain. Moreimportantly, the obtained mobilities, even over small areas, have oftenbeen unacceptably low or non-uniform compared to films formed by vaporphase techniques. (See, e.g., A. Stabel and J. P. Rabe, “Scanningtunneling microscopy of alkylated oligothiophenes at interfaces withgraphite,” Synthetic Metals, Vol. 67, 47 (1994); H. E. Katz et al.,“Synthesis, Solubility, and Field-Effect Mobility of Elongated andOxa-substituted α,ω-Dialkyl Thiophene Oligomers. Extension of ‘PolarIntermediate’ Synthetic Strategy and Solution Deposition on TransistorSubstrates,” Chemistry of Materials, Vol. 10, No. 2, 633 (1998); and H.Akimichi et al., “Field-effect transistors using alkyl substitutedoligothiophenes,” Appl. Phys. Lett., Vol. 58, No. 14, 1500 (1991).)

[0009] Spin-coating of oligomeric solutions onto a substrate has beenperformed more successfully, as reflected in C. D. Dimitrakopoulos etal., “trans-trans-2,5-Bis-[2-{5-(2,2′-bithienyl)} ethenyl]thiophene:synthesis, characterization, thin film deposition and fabrication oforganic field-effect transistors,” Synthetic Metals, Vol. 89, 193(1997); and F. Garnier et al., “Dihexylquarterthiophene, ATwo-Dimensional Liquid Crystal-like Organic Semiconductor with HighTransport Properties,” Chem. Mater., Vol. 10, 3334 (1998). Spin-coatingis wasteful, however, in that much of the solution flies off thesubstrate. Also, the technique is incompatible with the desired printingfabrication processes for organic TFTs, e.g., reel-to-reel processes ona flexible substrate, and is therefore more of a laboratory techniquethan a potential commercial process.

[0010] Thus, improved methods are desired for forming organicsemiconductor films from low molecular weight organic semiconductorcompounds. Of particular interest are non-spinning techniques fordepositing uniform, ordered organic films from solution.

SUMMARY OF THE INVENTION

[0011] A liquid phase technique, advantageously a non-spinning techniquesuch as solution casting, is used to form a crystalline orpolycrystalline organic semiconductor film from a solution of arelatively low molecular weight, e.g., oligomeric, organicsemiconducting compound. The resultant film exhibits, over a relativelylarge continuous area of at least 1 cm², advantageously at least 2 cm²,a desirable charge carrier mobility of at least about 10⁻⁴ cm²V⁻¹s⁻¹,advantageously at least 5×10⁻³ cm²V⁻¹s⁻¹ at room temperature. The filmadvantageously also exhibits an on/off ratio of at least 5,advantageously at least 100.

[0012] (As used herein, on/off ratio refers to the ratio of source-draincurrents measured for at least one value of the gate voltage less than100 volts on, and a gate voltage of zero volts off, in air, on adielectric having a capacitance of about 10⁻⁸ F/cm² and a resistivity ofat least 10¹⁰ ohm-cm, for a device operated in the saturation regime,using the same drain voltage to measure both currents. Organicsemiconductor film indicates a continuous layer of organic material on asubstrate that exhibits, over at least a portion thereof, a chargecarrier mobility of at least about 10⁻⁴ cm²V⁻¹ s⁻¹ at room temperature.Organic semiconductor compound, as used herein, indicates the molecularconstituent or constituents of an organic semiconductor film, where allsuch constituents have a molecular weight less than 1000.)

[0013] It has been found that there are several principles to apply inorder to successfully fabricate these organic semiconductor films fromsolutions of low molecular weight organic semiconductor compounds.First, nucleation of crystallites should be substantially restricted tothe interface between the solution and the substrate, as opposed tonucleation within the solution. Second, it is desirable to induce soliddeposition from solution before the pool of solution unacceptablycontracts in area. Third, overly fast crystallite growth at the edges ofthe pool of solution, relative to deposition across the pool area,should be avoided. Fourth, the film should have a substantiallyconnected morphology rather than isolated crystallites. These principlesprovide two-dimensional growth across the substrate and high uniformityand order in the resultant films. In one embodiment, these principlesare substantially met by using an elevated deposition temperature, adilute solution, and a substrate having a fluorinated surface. Theelevated temperature and dilute solution reduce nucleation within thesolution, while the fluorinated surface appears to promote nucleationover the solution-substrate interface.

BRIEF DESCRIPTION OF THE DRAWINGS

[0014]FIG. 1 illustrates a typical organic thin film transistor.

DETAILED DESCRIPTION OF THE INVENTION

[0015] According to the invention, a crystalline or polycrystallineorganic semiconductor film is formed by a liquid phase technique from asolution of a relatively low molecular weight, e.g., oligomeric, organicsemiconducting compound, advantageously from a non-spinning techniquesuch as solution casting. The process is performed by following fourbasic principles. First, nucleation of crystallites is substantiallyrestricted to the interface between the solution and the substrate, asopposed to nucleation within the solution. Second, solid deposition fromsolution begins before the pool of solution unacceptably contracts inarea. Third, materials and conditions that cause overly fast crystallitegrowth at the edges of the pool of solution are avoided. Fourth, thefilm should have a substantially connected morphology rather thanisolated crystallites. The invention applies these principles tosuccessfully fabricate high-quality organic semiconductor films from lowmolecular weight compounds.

[0016] To promote nucleation at the surface-solution interface, asopposed to within the solution, several guidelines are followed.Deposition conditions of high supersaturation are advantageouslyavoided, such that massive nucleation is unlikely. Temperature is keptrelatively high, solutions are kept dilute, and extremely insolublematerials (e.g., a solubility limit of <10 ppm at 100° C.) are avoided.In an exemplary embodiment, the solution poorly wets the substratesurface, e.g., a contact angle of at least 50° (such as by use of afluorinated surface, as discussed below). A high contact angle allows alarge volume of solution to be placed onto a given surface area, makingit possible to deposit enough solute from even a dilute solution.

[0017] Generally, contraction is also reduced or avoided when thecontact angle is high. Specifically, a high contact angle ensures thatthe pool of solution will not become overly thin at its edges duringevaporation. Such thin areas are unstable and tend to contract. However,in some cases, it may be possible to deposit a useful film according tothe invention with a low contact angle.

[0018] As mentioned above, it is advantageous to use solutes that tendto avoid supersaturation before nucleating. This characteristic is ableto be tested by taking a sample of the solution and monitoring whetherthe solute crystallizes gradually at the temperature or concentration ofdissolution or whether the concentration moves past saturationconditions well before crystallization occurs. The latter would suggestthat supersaturation occurs before deposition, which would lead to largedroplet shrinkage followed by sudden deposition of solid in a smallarea, neither of which is desirable for fabricating the organicsemiconductor films of the invention. Further, preferential wetting ofcrystallites by the solution, relative to the substrate surface, isdesirable because deposited crystallites would then tend to hold thepool of solution in place, thereby inhibiting shrinkage in area. Suchpreferential wetting would be expected if the contact angle of solutionon the deposited material is less than the contact angle of solution onthe substrate surface. Moreover, if the solution droplet becomes thinenough while still substantially maintaining its original area coverage,crystal growth would become confined to two-dimensional space, whichfavors a desirable morphology (in the case of such thinning, it may bepossible to obtain a useful film with a low contact angle).

[0019] Growth at the edge of a solution pool is determined by rates ofnucleation and of enlargement of the crystal nuclei. The variety offactors that influence such nucleation and enlargement have been studiedextensively, but the particular relationships have yet to be fullyunderstood. In the invention, however, it has been observed thatcompounds with more polar or quadrupolar aromatic or heteroaromatic ringsystems, such as bithiazole, appear to deposit from solutionpreferentially, and undesirably, at nuclei formed at a pool boundary,particularly at temperatures only slightly higher than ambient. Incontrast, less polar, thiophene systems do not appear to exhibit suchpreferential nucleation along a pool boundary. A simple test is usefulfor determining materials suitable for the invention which tend to avoidfast growth at the edge of a solution pool. Specifically, a drop ofsolution is placed onto a substrate and allowed to evaporate/deposit. Ifa pronounced ring or rings form, separated by or encirclingsubstantially empty regions, the material system is unlikely to promotethe desired uniform, two-dimensional growth, but will instead tend toform distinct aggregates of material.

[0020] The desired interconnected morphology is generally attained bymeeting the previously-discussed guidelines. In particular,two-dimensional growth provided by avoidance of edge-preferentialnucleation contributes to interconnectivity.

[0021] Any substrate/solution systems, using a solute of organicmaterial capable of exhibiting semiconductor properties, meeting theseprinciples are expected to provide desirable properties, e.g., anorganic semiconductor film exhibiting, over a relatively largecontinuous area of at least 1 cm², advantageously at least 2 cm², adesirable charge carrier mobility of at least about 10⁻⁴ cm²V⁻¹s⁻¹,advantageously at least 5×10⁻³ cm²V⁻¹s⁻¹ at room temperature.Advantageously, the uniformity of the continuous area is such that 80%of this continuous area exhibits a charge carrier mobility within afactor of two of the average charge carrier mobility of the continuousarea. This continuous area advantageously also exhibits an on/off ratioof at least 5, advantageously at least 100.

[0022] Advantageously, a fluorinated organic surface is provided topromote attainment of these principles, particularly when thesemiconductor compound is not fluorinated. As mentioned above,fluorination promotes such attainment by decreasing the wettability ofthe substrate surface, particularly by a non-fluorinated solvent,thereby providing a high contact angle (e.g., at least 50°). To providethe fluorinated substrate, it is possible to treat the surface of anon-fluorinated substrate with a fluorinated compound. Techniques fordoing so include dipping the substrate into a reagent that effects thebinding of fluorinated groups such as fluoroalkyl chains to thesubstrate, evaporating such a reagent onto the substrate, or spinningonto a substrate a material containing such groups. It is also possiblefor these surface-treatment techniques to include removal of solvents orby-products of the binding step, e.g., by vaporization or rinsing.Instead of depositing a fluorinated material onto a substrate, it isalso possible to provide a fluorinated substrate material, e.g., adielectric polymeric material rich in fluoroalkyl chains.

[0023] The fluorine concentration on the substrate surface should besufficient to alter the wetting properties of the substrate surfacerelative to the solution. In particular, treatment of non-fluorinatedsubstrates by a fluorinated silane has been found to be advantageous,particularly where the fluorinated silane is partially oligomerizedprior to application. The partial oligomerization is generally performedeither by (a) a reaction with sufficient water to cause a degree ofoligomerization of about 1.2 to about 3 (leading to a product referredto as oligomerized), or (b) by partially gelling the silane, e.g., withaqueous HCl, and using the xylene-soluble fraction of the resultantmaterial (leading to a product referred to as partly gelled). (Usefulfluorinated silanes contain a silicon atom having ≧1 leaving groupattached thereto, and an organic group not on the leaving group thatprovides sufficient CF groups to change the contact angle of a solutionby at least 10°.) One such fluorinated silane is C₈F₁₇C₂H₄Si(OEt)₃. Forfabrication of organic circuits, the substrate is, or has a surfacelayer of, an insulating material, typically exhibiting an electricalresistivity of at least 10¹⁰ ohm-cm. Insulating materials include, butare not limited to, silicon dioxide, polyimide, and polyvinylphenol.

[0024] A variety of low molecular weight organic semiconductingcompounds (molecular weight less than 1000) capable of forming anorganic semiconducting film are suitable for use in the invention,provided the guidelines discussed herein are able to be met. Some usefulcompounds are known in the art. Non-polar thiophene oligomers, which arep-type semiconductors, appear to be particularly suitable for use.Specific p-type organic semiconductor compounds useful in the invention,particularly with a fluorinated substrate surface, includeα,ω-dihexyl-α-sexithiophene (DHα6T), α,ω-dihexyl-α-quinquethiophene(DHα5T), and α,ω-bis(3-butoxypropyl)-α6T.

[0025] It is also possible to use an n-type organic semiconductor. Inparticular, as discussed in co-filed, co-assigned application entitled“Device Comprising N-Channel Semiconductor Material” (our referenceKatz-Li-Lovinger 31-2-3) it is possible to form useful n-channel filmsfrom liquid phase deposition. Contemplated compounds include fused-ringtetracarboxylic diimides, including naphthalene 1,4,5,8 tetracarboxylicacid diimides, naphthalene 2,3,6,7 tetracarboxylic acid diimides,anthracene 2,3,6,7-tetracarboxylic acid diimides, and heterocyclicvariants thereof. One advantageous group of compounds is naphthalene1,4,5,8-tetracarboxylic acid diimides with linear chains of four totwelve saturated atoms, generally carbon atoms, affixed to each of thetwo imide nitrogens. Advantageously, at least a portion of thesubstituents on the carbons of the linear chains are fluorosubstituents, which appear to improve the capacity for operation in air.

[0026] A suitable solvent is selected based on the particular organicsemiconducting compound used, as well as the wetting, crystalnucleation, and crystal growth on the substrate surface. Many organicsemiconducting materials are relatively insoluble, with a solubilityrange in a solvent of about 10 to about 1,000 ppm. Moderately polararomatic solvents are generally used to ensure adequate solubility. (Amoderately polar aromatic solvent indicates a compound containing anaromatic or heteroaromatic ring, typically with alkyl and/or halogensubstituents.) Suitable solvents include, but are not limited to,toluene, chlorobenzene, 1,2,4-trichlorobenzene, and 3-methylthiophene.Useful solvents for the naphthalene or anthracene based-compoundsinclude moderately polar aromatic solvents containingtrifluoromethylphenyl groups.

[0027] The device of the invention is typically a circuit containingorganic semiconductor films, with such films optionally being the activematerials of one or more thin film transistors. (See, e.g., H. E. Katz,“Organic molecular solids as thin film transistor semiconductors,” J.Mater. Chem., Vol. 7, No. 3, 369 (1997); and H. E. Katz et al., “Oligo-and Polythiophene Field Effect Transistors,” Chapter 9, Handbook ofOligo- and Polythiophenes, D. Fichou, ed., Wiley-VCH (1999).) A processfor forming such a device involves providing at least one substrate,electrode material and/or dielectric material, and depositing one ormore organic semiconductor films onto the substrate, electrode, and/ordielectric. For ease of processing, it is possible to use a substrate ofa polymeric insulating material, such as a polyimide. One desirablefabrication process is a reel-to-reel process, in which a continuoussheet of substrate material is advanced in stages, with one or morematerials deposited, patterned, or modified at each stage, e.g., byprinting techniques. According to the invention, it would be possible toapply a film or pool of a solution containing one or more organicsemiconductor compounds, e.g., by dispensing through a valve, byspraying through a nozzle, or by a printing technique, and evaporatingthe solvent to leave an organic semiconductor film. It is possible toheat the substrate, or provide a vacuum before, during, or afterapplication of the solution. It is thereby possible to form an organicsemiconductor film without the need to separate the region of thesubstrate receiving the film from the rest of the sheet, such thatimproved process efficiency and lower cost are achieved.

[0028] Moreover, using both p-channel and n-channel organicsemiconductor materials, it is possible, according to the invention, tofabricate a complementary circuit by liquid phase deposition. (See,e.g., A. Dodabalapur et al., “Complementary circuits with organictransistors,” Appl. Phys. Lett., Vol. 69, No. 27, 4227 (1996).) Inparticular, simple components such as inverters have been realized usingcomplementary circuit architecture. Advantages of complementarycircuits, relative to ordinary TFT circuits, include lower powerdissipation, longer lifetime, and better tolerance of noise.

[0029] The invention will be further clarified by the followingexamples, which are intended to be exemplary.

EXAMPLES 1 AND 2

[0030] Procedure:

[0031] Semiconductor compounds used were fabricated according tostandard techniques. Chlorobenzene and 1,2,4-trichlorobenzene werewashed with concentrated sulfuric acid and aqueous sodium carbonate anddistilled from P₂O₅. Other solvents were the purest available commercialgrades.

[0032] Substrates were: silicon dioxide (heavily phosphorus-doped(n-type) silicon with 3000 Å of thermal oxide thereon); Amoco polyimide(indium tin oxide glass coated with about 1 to 2 μm of Amoco Ultradel™photocurable polyimide, spun from 8% w/v γ-butyrolacetone solution at1200 rpm, baked for about 1 hour at 130° C., and UV-cured for about 30minutes); JSR polyimide (about 1 to 2 μm of JSR Optimer™ AL3046polyimide, spun from 8% w/v γ-butyrolacetone solution at 1400 rpm, bakedfor about 1 hour at 120° C.); or polyvinylphenol on SiO₂/Si substrates(about 1 to 2 μm of Aldrich polyvinylphenol with an average molecularweight of ca. 20,000, spun from an 8% w/v acetone solution at 1200 rpm).

[0033] Fluorinated surfaces were: fluorinated silane, either partlygelled or oligomerized, the silane deposited by immersing substrates in1% C₈F₁₇C₂H₄Si(OEt)₃ reagent solution in xylene at 80° C. for 10minutes, followed by rinsing with toluene (oligomerized silane waspartially hydrolyzed by heating with a 5% solution of 1.2N HCl inethanol (containing 0.25 to 0.5 equiv of water), adding 10 volumes oftoluene, and reheating to boil out the ethanol); or fluoroacrylate(provided by spin-coating an overlayer of 3M Fluoroacrylate Coating 722,2% solution in volatile fluorinated at 1200 rpm).

[0034] Semiconductor films were applied by transferring 0.1 to 0.3 mL ofpreheated solution with a heated pipette onto substrates that had beenthermally equilibrated in a vacuum oven, at temperatures noted below andat atmospheric pressure. A vacuum of about 0.2 atm was pulled for 1 to 2hours—until the solvent was removed. Gold electrodes were deposited byevaporation through shadow masks. Carbon electrodes were painted from anisopropanol suspension using a paintbrush. Characterization wasperformed by conventional techniques.

Example 1

[0035] DHα6T was deposited onto both untreated and fluorinatedsubstrates from chlorobenzene at 60° C.±10° C. For these samples, TableI presents the concentration of the DHα6T in solution, the substrate,the surface coating (if any), the mobility, and the surface area overwhich the mobility was exhibited. TABLE I Area Concen- exhibitingtration Surface Mobility mobility (ppm) Substrate Coating (cm²/V-sec)(cm²) 30 Amoco PI — 0.005-0.1  <0.2 50 Amoco PI — ˜0.001 <0.2 25 AmocoPI 3M722 0.05 2-3 50 Amoco PI Fluorinated Silane 0.003-0.005 >1 (partlygelled) 50 Amoco PI Fluorinated Silane 0.06-0.08 >1 (oligomerized) 50Amoco PI Octadecyltrimethoxy — <0.2 silane (non-fluorinated) 60 SiO₂/Si— 0.1 <0.2 75 Amoco P1 Fluorinated Silane 0.03 2 (oligomerized)

Example 2

[0036] DHα5T was deposited onto both untreated and fluorinatedsubstrates from several solutions at a concentration of 400 ppm at 60 to70° C. For the samples, Table II presents the particular solvent, thesubstrate, the surface coating (if any), the mobility, and the area overwhich the mobility was exhibited. TABLE II Area exhibiting SurfaceMobility mobility Solvent Substrate Coating (cm²/V-sec) (cm²) TolueneSiO₂/Si — ≦0.17  >1^(a) Toluene SiO₂/Si Fluorinated Silane 0.05-0.06>1^(b) (oligomerized) Chloro- SiO₂/Si — ≦0.02  >1^(a) benzene Chloro-SiO₂/Si Fluorinated Silane 0.03-0.04 >1^(b) benzene (oligomerized)Toluene JSR PI/SiO₂/Si — 0.03  0.5^(a) Toluene JSR PI/SiO₂/SiFluorinated Silane 0.04 >1^(b) (oligomerized) Toluene Polyvinyiphenol/ —0.07  0.5^(a) SiO₂/Si Toluene Polyvinylphenol/ Fluorinated Silane 0.06>1^(b) SiO₂/Si (oligomerized) Chloro- SiO₂/Si 3M 722 0.03-0.04  1^(b)benzene

Example 3

[0037] A solution ofN,N′-bis(1H,1H-perfluorooctyl)naphthalene-1,4,5,8-tetracarboxylicdiimide, 400 parts per million by weight, in α,α,α-trifluorotoluene, wasprepared by gentle heating. This solution was cast onto a silicon/SiO₂substrate that had been preheated to about 100° C. The solventevaporated within about 2 minutes. A 1 cm² region of the substratebecame coated with a thin deposit that showed significant n-channelactivity when tested with gold electrodes. The highest mobility obtainedwas 0.07 cm²/Vs measured in air with a device width/length ratio of 1.7,although other parts of the area showed mobility an order of magnitudelower.

[0038] An uncoated region of the substrate was used to cast a film ofDHα5T from a 400 ppm toluene solution at 100° C. under vacuum. Goldelectrodes were deposited on the thienyl compound. Inverter circuitswere constructed by connecting the drain electrode of a diimide devicewith the drain electrode of a thienyl device, and forming an outputcontact from the connection. The effective W/L ratio of the thienyldevice ranged from 1.7 to 0.1. The output was switched between ±0-10volts and ±68-98 volts by sweeping the gate over a range of 60 volts andapplying a voltage of 100 volts to the source of the thienyl device, or−100 volts to the source of the diimide device. Output voltagedifferentials as high as 95 volts and gains as high as 10 were observed.

[0039] Other embodiments of the invention will be apparent to thoseskilled in the art from consideration of the specification and practiceof the invention disclosed herein.

What is claimed is:
 1. A process for fabricating an organic circuit,comprising the steps of: providing a substrate; providing a solutioncomprising a solvent and an organic semiconductor compound; applying thesolution to the substrate surface by a non-spinning technique; andevaporating the solvent to form an organic semiconductor film comprisinga continuous area greater than 1 cm² that exhibits a charge carriermobility of at least about 10⁻⁴ cm²V⁻¹s⁻¹ at room temperature.
 2. Theprocess of claim 1 , wherein the continuous area exhibits an on/offratio of at least
 5. 3. The device of claim 1 , wherein the continuousarea greater than 1 cm² exhibits a charge carrier mobility of at leastabout 5×10⁻³ cm²V⁻¹s⁻¹ at room temperature
 4. The process of claim 1 ,wherein the substrate comprises a fluorinated surface.
 5. The process ofclaim 4 , wherein the fluorinated surface comprises afluorine-containing compound deposited on the substrate.
 6. The processof claim 5 , wherein the fluorine-containing compound is a fluorinatedsilane.
 7. The process of claim 6 , wherein the substrate furthercomprises a polymeric material underlying the fluorinated surface. 8.The process of claim 4 , wherein the contact angle between the solutionand the fluorinated surface is at least 50°.
 9. The process of claim 1 ,wherein the organic semiconductor compound is selected fromα,ω-dihexyl-α-sexithiophene, α,ω-dihexyl-α-quinquethiophene,α,ω-bis(3-butoxypropyl)-α-sexithiophene, and naphthalene 1,4,5,8tetracarboxylic acid diimides.
 10. The process of claim 1 , wherein thefilm comprises a continuous area greater than 2 cm² that exhibits acharge carrier mobility of at least about 10⁻⁴ cm²V⁻¹s⁻¹ at roomtemperature.
 11. The process of claim 10 , wherein the continuous areaexhibits an on/off ratio of at least
 5. 12. The process of claim 1 ,wherein 80% of the continuous area exhibits a charge carrier mobilitywithin a factor of two of the average charge carrier mobility of thecontinuous area.
 13. The process of claim 1 , wherein the solvent is amoderately polar aromatic solvent.
 14. The process of claim 13 , whereinthe solubility of the organic semiconducting material in the solvent isabout 10 to about 1,000 ppm.
 15. The process of claim 1 , wherein thesolution is applied by solution casting.
 16. The process of claim 15 ,further comprising at least one of heating the substrate duringapplication and applying a vacuum.
 17. A device comprising: a substratecomprising a fluorinated surface; and an organic semiconductor filmdeposited on the substrate, the film formed from a organic semiconductorcompound, wherein the film comprises a continuous area greater than 1cm² that exhibits a charge carrier mobility of at least about 10⁻⁴cm²V⁻¹s⁻¹ at room temperature.
 18. The device of claim 17 , wherein thecontinuous area exhibits an on/off ratio of at least
 5. 19. The deviceof claim 17 , wherein the continuous area greater than 1 cm² exhibits acharge carrier mobility of at least about 5×10⁻³ cm²V⁻¹s⁻¹ at roomtemperature
 20. The device of claim 17 , wherein the fluorinated surfacecomprises a fluorinated silane.
 21. The device of claim 20 , wherein thesubstrate further comprises a polymeric material underlying thefluorinated surface.
 22. The device of claim 17 , wherein the organicsemiconductor compound is selected from α,ω-dihexyl-α-sexithiophene,α,ω-dihexyl-α-quinquethiophene, α,ω-bis(3-butoxypropyl)-α-sexithiophene,and naphthalene 1,4,5,8 tetracarboxylic acid diimides.
 23. The device ofclaim 17 , wherein the film comprises a continuous area greater than 2Cm² that exhibits a charge carrier mobility of at least about 10⁻⁴cm²V⁻¹s⁻¹ at room temperature.
 24. The device of claim 17 , wherein 80%of the continuous area exhibits a charge carrier mobility within afactor of two of the average charge carrier mobility of the continuousarea.